/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.utils.writelog;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
import java.util.zip.CRC32;

/**
 * LogWriter writes the binary logs into a file using FileChannel together with check sums of each
 * log calculated using CRC32.
 */
public class LogWriter implements ILogWriter {
    private static final Logger logger = LoggerFactory.getLogger(LogWriter.class);

    private final File logFile;
    private FileOutputStream fileOutputStream;
    private FileChannel channel;
    private final CRC32 checkSummer = new CRC32();
    private final ByteBuffer lengthBuffer = ByteBuffer.allocate(4);
    private final ByteBuffer checkSumBuffer = ByteBuffer.allocate(8);
    private final boolean forceEachWrite;

    public LogWriter(File logFile, boolean forceEachWrite) throws FileNotFoundException {
        this.logFile = logFile;
        this.forceEachWrite = forceEachWrite;

        fileOutputStream = new FileOutputStream(logFile, true);
        channel = fileOutputStream.getChannel();
    }

    @Override
    public void write(ByteBuffer logBuffer) throws IOException {
        if (channel == null) {
            fileOutputStream = new FileOutputStream(logFile, true);
            channel = fileOutputStream.getChannel();
        }
        logBuffer.flip();
        int logSize = logBuffer.limit();
        // 4 bytes size and 8 bytes check sum

        checkSummer.reset();
        checkSummer.update(logBuffer);
        long checkSum = checkSummer.getValue();

        logBuffer.flip();

        lengthBuffer.clear();
        checkSumBuffer.clear();
        lengthBuffer.putInt(logSize);
        checkSumBuffer.putLong(checkSum);
        lengthBuffer.flip();
        checkSumBuffer.flip();

        try {
            channel.write(lengthBuffer);
            channel.write(logBuffer);
            channel.write(checkSumBuffer);

            if (this.forceEachWrite) {
                channel.force(true);
            }
        } catch (ClosedChannelException ignored) {
            logger.warn("someone interrupt current thread, so no need to do write for io safety");
        }
    }

    @Override
    public void force() throws IOException {
        if (channel != null && channel.isOpen()) {
            channel.force(true);
        }
    }

    @Override
    public void close() throws IOException {
        if (channel != null) {
            if (channel.isOpen()) {
                channel.force(true);
            }
            fileOutputStream.close();
            fileOutputStream = null;
            channel.close();
            channel = null;
        }
    }

    @Override
    public String toString() {
        return "LogWriter{" + "logFile=" + logFile + '}';
    }
}
